SYNTHESIS AND CHARACTERIZATION OF HIGH-MOLECULAR-WEIGHT POLY(1,5-DIOXEPAN-2-ONE) WITH NARROW MOLECULAR-WEIGHT DISTRIBUTION

Ring-opening polymerization of 1,5-dioxepan-2-one (DXO) initiated with aluminium isopropoxide in tetrahydrofuran (THF) solution and in bulk has been investigated. An improved monomer purification procedure is p resented which makes it possible to synthesize high molecular weight p oly(DXO) with a narrow molecular weight distribution. The kinetic depe ndence on parameters such as polymerization temperature, the presence of Lewis bases and water impurities is discussed. The activation energ ies (E(a)) of the solution polymerization with and without 1 molar equ ivalent of pyridine (relative amount of initiator) were found to be 42 .2 and 44.0kJmol(-1), respectively. The addition of a Lewis base (pyri dine) did not influence the polymerization kinetics and transesterific ation reactions to any great extent. Bulk polymerization proceeds rapi dly to full conversion and leads to poly(DXO) with a controlled molecu lar weight and a narrow molecular weight distribution. The Mark-Houwin k relationship in THF at 25 degrees C was determined; values of consta nts were K = 1.1 x 10(-4) dlg(-1) and a = 0.766.